The present invention relates to determining the rotation angle of a shaft in an aircraft. In particular the present invention relates to a device for determining the rotation angle of a shaft in an aircraft; to an aircraft comprising a corresponding device; to the use of a corresponding device in an aircraft; and to a method for determining the rotation angle of a shaft in an aircraft.
The system for operating a brake flap or a landing flap or landing slat in an aircraft forms part of the safety-critical systems within the aircraft. Nowadays electromechanical systems for operating the landing flaps or landing slats are used, which systems are designed so as to be redundant if need be and have proven to be highly reliable. In order to operate the landing flaps or landing slats, generally speaking mechanical shaft systems for transmission of the rotational forces are used. In order to prevent the occurrence of asymmetries in the flap positions and in order to still be able to adjust all the flaps should a drive motor fail, all flaps are connected to central shafting.
The position of the flaps is measured by way of two or even four independent position pickup units (PPUs) for each flap segment on the shaft. These sensors are located at the ends of the shaft part so as to detect differences in the absolute positions of the two shaft ends, and in this way provide information about the forces acting on the mechanism. In the normal state the servo motors are highly synchronised, in other words no forces act on the shaft.
If, in the case of a malfunction, one of the PPUs fails, in the state of the art the motor that is seated on the corresponding shaft end is switched off because it is no longer possible to measure the position, and because the motor would then not be synchronised. Possibly a so-called force fight between the two motors would develop, and at some stage the shaft would be destroyed. On the other hand this also means that a fault-free and properly functioning component (namely the motor) is switched off because of a malfunction of some other component so that the availability of the system may be thus reduced by 50%. Furthermore, the dynamics and agility of the system may be reduced by 50% because the remaining motor then runs only at half its possible rotary speed. In order to maintain synchronicity, the same also applies to the other wing.